In the state of art, a disk brake is well-known that has a shim (shim plate) for anti-brake shudder provided between a back metal of a brake pad and a pressuring element (a piston or a pawl portion of a cylinder) for pressing the brake pad against a disk rotor. JP2003-329067 A discloses this type of a disk brake, in which on the shim are formed a plural of projections (dimples) so as to establish contact between the pressuring element and the projections of the shim under a low pressuring force at a low braking force. JP4-138137 A discloses a technique for reducing brake shudder by providing a shim on a back metal such that the shim can move with respect to the back metal and thus permitting movement of the shim with respect to the back metal during a braking operation.
In general, on such type of a disk brake are provided stoppers for limiting the range of the movement of the shim in order to prevent unlimited movement of the shim with respect to the back metal. For example, in a structure in which the shim has hooks hooked at the perimeter of the back metal, on the perimeter of the back metal are formed wall portions for limiting the movement of the hooks beyond a predetermined amount. With such a structure, forces are applied to the shim by the pressuring element and the wall portion during a braking operation; however, depending on a positional relationship between points of action of these forces, non-uniformity in the distribution of pressuring forces on the shim applied by the pressuring element may occur, causing a bottleneck in reducing brake shudder.